Page | 1

Cooperation between
Fukushima Prefecture and the IAEA
In the Area of Radiation Monitoring, Remediationand Waste Management, Following the
Fukushima Daiichi Nuclear Power Plant Accident(Fukushima Prefecture Initiative Projects)

INTERIM REPORT(2013–2015)【Detailed version】(Temporary translation)

2016
Fukushima Prefecture2 | Page

Page | 3

Contents
Introduction ............................................................................................................................ 5
1. FIP1: Survey of radionuclide movement in rivers and lakes ................................................ 9
1.1. Introduction ...................................................................................................................... 9
1.2. Methods .......................................................................................................................... 10
1.3. Results ............................................................................................................................ 14
1.4. Conclusion ...................................................................................................................... 21
2. FIP2: Survey of radionuclide movement with wildlife ........................................................ 222.1. Purpose ........................................................................................................................... 222.2. Implementation Details ................................................................................................... 222.3. Results ............................................................................................................................ 24
3. FIP3: Project for studying decontamination technology for rivers and lakes...................... 32
3.1. Purpose ........................................................................................................................... 32
3.2. Details of Implementation ............................................................................................... 32
4. FIP4: Development of environmental mapping technology with GPS walking surveys ...... 44
4.1. Purpose ........................................................................................................................... 44
4.2. Implementation Details ................................................................................................... 46
4.3. Summary ........................................................................................................................ 56
5. FIP5: Project for the study of promoting the proper treatment of waste containing
radioactive materials at municipal solid-waste incinerators ................................................... 57
5.1. Purpose ........................................................................................................................... 57
5.2. Implementation Details ................................................................................................... 58
5.3. Results and Discussion .................................................................................................... 65

4 | Page

Page | 5

Introduction
Severe damage was caused by the Tohoku Earthquake that struck on March 11, 2011 and theaccompanying accident at the Fukushima Daiichi Nuclear Power Plant operated by the Tokyo
Electric Power Company. Restoring the environment after this unprecedented nuclear disasterand creating an environment in which residents of Fukushima Prefecture can live with peace ofmind well into the future have become pressing challenges.
It is critical to gather the wisdom of the world and to work to overcome these challenges, andFukushima Prefecture thus decided to collaborate with the International Atomic Energy Agency(IAEA), which has advanced knowledge in fields concerning nuclear technology. A
memorandum of cooperation between Fukushima Prefecture and the IAEA was signed in
December 2012.
According to this memorandum, practical arrangements in the fields of decontamination andradiation monitoring between Fukushima Prefecture and the IAEA were signed on the same date.
(Projects based on these arrangements are referred to as FCPs.)
Following this, additional arrangements were signed for five projects (referred to below as
FIPs) proposed by Fukushima Prefecture in April and October 2013 as a new framework withwhich to receive support from the IAEA for projects implemented by Fukushima Prefecture.
The five FIPs are the projects and activities listed below.
1) Survey of radionuclide movement in rivers and lakes2) Survey of radionuclide movement with wildlife
3) Project for studying decontamination technology for rivers and lakes
4) Development of environmental mapping technology using GPS walking surveys
5) Project for the study of promoting the proper treatment of waste containing
radioactive materials at municipal solid waste incinerators
FIPs began in 2013, the year in which the practical arrangements were signed, and it was
decided to publish this interim report because 3 years have passed since.
Fukushima Prefecture has received various forms of support from the IAEA over the 3 years,
the major contents of which are described below.

6 | Page

Contents of major support received from the IAEA
1) Survey of radionuclide movement in rivers and lakes
・Provision of a TODAM (Time-dependent, One-directional, Degradation and Migrational)
model, which is a numerical simulation code of contaminant migration in a river network,for the quantitative estimation of radionuclides deposited in rivers.
・Technical guidance on the selection of monitoring points and monitoring items, and an
indication of the importance of continuous monitoring at each monitoring point, basedon previous studies for Chernobyl and Mayak.
・Regarding monitoring data obtained by Fukushima Prefecture, advice that measuring Kdvalues and ion concentrations (especially K+ and NH4+) in river water at each monitoring
point is important for the use of numerical models such as the TODAM model.
・Advice on the effectiveness of combining monitoring and models and adding small lakes
and marshes as subjects of research in advancing future research on the dynamics ofradioactive substances in rivers.
2) Survey of radionuclide movement with wildlife
・Provision of foreign literature describing the relationship between wild animals andradionuclides, such as the state of radiocaesium in the muscle tissue of wild animals
including boars and deer in various regions following the Chernobyl nuclear disaster andchanges in radiocaesium levels in the bodies of birds, such as the American gallinule andAmerican wood duck, at the Savannah River Ecology Laboratory.
・Provision of information about the latest scientific results concerning the bioaccumulationof radiocaesium from experts investigating the relationship between wild animals andradioactive substances.
・Advice on the discussion of study results and data analysis methods, such as the potentialthat mushrooms are the cause of a high radiocaesium concentration in boars of
Fukushima Prefecture, arising from the fact that mushrooms (deer truffles) were found tobe the cause of a high radiocaesium concentration in the muscle tissue of European
boars.
3) Project for studying decontamination technology for rivers and lakes
・ Provision of information concerning the environmental dynamics of radioactive
substances in rivers, lakes, and marshes of various countries.
・ Provision of case studies of environmental remediation measures, such as thedecontamination of radioactive substances in rivers, lakes, and marshes of various
countries, including countermeasures for the inflow of high concentrations of radioactive

Page | 7

substances to the Pripyat River and measures for suppressing the inflow of radioactive
substances to the Kiev Reservoir.
・Advice on the effective implementation of verification tests targeting riverbeds, including
the necessity of survey items, survey points, and advance simulations for studies
confirming reduced effects of air dose rates and the necessity of survey items (e.g., thesize distribution of particles in suspended phases) and weeding test sites when evaluatingrecontamination.
・Regarding studies of effective radioactive-substance countermeasures targeting river parks,
advice to reference past flooding records when selecting survey sites and advice that thedredging and construction of embankments, as well as grit chambers in upstream basins,are effective at sites where there is a concern of recontamination.
4) Development of environmental mapping technology using GPS walking surveys
・Provision of information about efforts made by institutions such as the United States
Environmental Protection Agency and Lawrence Berkeley National Laboratory
regarding local radiation dose mapping.
・Advice that inverse-distance weighting (IDW) is more appropriate than Kriging as ameans of interpolation for walking surveys using the GIS, and that considerations must
be made for the shielding effect of buildings and the like.
・Advice to judge measurement conditions of walking surveys by the situation at eachmeasurement point, as it is not always necessary to set uniform measuring conditions.
5) Project for the study of promoting the proper treatment of waste containing
radioactive materials at municipal solid-waste incinerators
・Provision of information on treatment methods employed in other countries for fly ash,treatment methods employed in other countries for low-level radioactive waste (i.e.,
incineration, melting treatment of metal, and plasma melting), and instruments formeasuring the concentrations of radioactive substances in waste.
・Technical advice about the incineration of general waste, such as the necessity of studies
conducted from the perspective of the caesium balance of payments, the importance ofthe comparative analysis of actual verification test data and model analysis results, andthe necessity of identifying test conditions and assessing waste quality.
・Advice about the importance of countermeasures to the generation of hydrogen fluoride in
the mixed incineration of bag filters (made from Teflon).
・Advice on the necessity of checking the safety (e.g. exposure protection and management)of facility workers.

8 | Page

In this manner, Fukushima Prefecture has implemented FIPs with support from the IAEA.
The interim report including results of FIPs is provided as follows.
＜This document is issued under the authority and responsibility of the Fukushima Prefecture. ＞

Page | 9

1. FIP1: Survey of radionuclide movement in rivers and lakes
Summary
It is important to provide information necessary for the safe use of river water in the area
contaminated by radionuclides. We conducted a survey of rivers flowing through Fukushima
Prefecture with the purpose of understanding the dynamics of radionuclides in rivers andverifying dynamics forecasting with numerical models.
To forecast radionuclide dynamics with models, we established data collection necessary
for application of the TODAM model to the Hirose River and a monitoring network necessary
for verification of dynamics forecasting. Additionally, we conducted a dynamics survey ofsuspended state radiocaesium adsorbed on small particles that flow downstream in the Abukuma
River System and major rivers in the Hamadori area. As a result, we observed a decreasing trend
in particulate radiocaesium and regional variation in the rate of decreasing radiocaesium
concentration depending on land use in the basin.

1.1. Introduction
River water is widely used for tap
water and agricultural water. Owing to theaccidentattheFukushima

DaiichiNuclear Power Plant in 2011, Fukushima
Prefecture was widely contaminated byradionuclides. Because basins have been
contaminated, it is an important challenge
for us to understand the dynamics ofradionuclides in rivers and to provide
information necessary for the safe use ofriver water. It is also important to grasp
the dynamics of radiocaesium in thefollowing two forms. In the case thatradiocaesium is adsorbed onto suspended
sediments (i.e., the so-called particulate
form of radiocaesium), the effect of

Figure 1: Schematic view of radiocaesium
dynamics in river basinsredeposition during floods on the air doseis a concern. Meanwhile, it is also necessary to consider migration through agricultural crops
and the ecosystem when radiocaesium flows in a dissolved form (Figure 1). We therefore
studied rivers flowing through Fukushima Prefecture to clarify the dynamics of radionuclides in10 | Page

rivers, with the additional purpose of verifying the forecasting of dynamics of radionuclides
with numerical models using the monitoring data obtained.

1.2. Methods(1) Survey in the Hirose River Basin
We conducted a 3-year study of the Hirose River and its tributaries beginning in 2013.
Figure 2(a) shows the inventory of caesium-137 on July 2, 2011 in the basin. Near the basinboundaries on the southeast side, the area marked red has been checked, and there is a highamount of radiocaesium deposition near the basin boundaries on the southeast side and in the
Nuno River Basin and Oguni River Basin, which are basins of two tributaries of the Hirose
River (Table 1).

Table 1: Relationship between the catchment area and average caesium-137
inventory for the Hirose River, Nuno River, and Oguni River

We collected samples at various sites in Figure 2(a); the primary monitored items
are given in Table 2. Among the monitored items, the radiocaesium concentration inwater samples was measured after the following pretreatment. Raw water was filteredusing a membrane filter with a pore size of 0.45 µm. Ten-liter specimens of raw waterand filtrate were passed at a rate of 20 mL/minute through columns (inner diameter: 5
cm, height: 40 cm) filled with 40 g each of anion exchange resin and cation exchange
resin. After passing the specimens through the columns, the resin was dried at 105 °C,
sealed in specialized containers (U-8), and used as specimens for measurement. The
concentration of radiocaesium was measured with methods conforming to γ-ray
Spectrometry using a Germanium Semiconductor Detector (MEXT, 1992).

Page | 11

Table 2: Major observation items

Abukuma river

Figure 2: Map of the locations of monitoring sites and caesium-137 inventory on July 2,
2011(a) Hirose River Basin. (b) Area subject to a wide-area survey. Numbers in the figure
correspond to the site numbers in Table 3.
* Source: Results of the Third Airborne Monitoring Survey conducted by MEXT (2011)
http://radioactivity.nsr.go.jp/en/contents/5000/4182/24/1304797_0708e.pdf
However, (b) is complemented using results of airborne monitoring by prefecture(http://emdb.jaea.go.jp/emdb/en/portals/b224/) and Results of Radioactive Caesium
Deposition of the First Unmanned Helicopter Monitoring within the 3 km Radius from the
Fukushima Dai-ichi NPP (http://emdb.jaea.go.jp/emdb/en/portals/b225/) for areas outside
the survey range of the Third Airborne Monitoring Survey.

12 | Page

(2) Wide-area survey on the riverine transport of radiocaesium
Since 2015, we have conducted multi-point river surveys of the Abukuma River Systemand eight river systems in the Hamadori area. Figure 2(b) shows a map of the locations ofmonitoring sites and the caesium-137 inventory. Whereas the survey in the Hirose River was adetailed survey of a single basin, the purpose of this wide-area survey is to understand the effectof features of the basins on the long-term changes of radiocaesium dynamics by continuingsurveys in multiple rivers employing the same methods. This survey inherited a survey
conducted by the University of Tsukuba and commissioned by MEXT and the Nuclear
Regulation Authority (NRA) until the end of the 2014 fiscal year. In this report, we introduce
results together with past monitoring data. At each monitoring point, we set up a suspended
sediment sampler to collect suspended sediment samples, a turbidity meter to measure theturbidity of river water, and a water level meter to measure water depth. At some sites, we use
water level data recorded by Fukushima Prefecture and the Ministry of Land, Infrastructure,
Transport, and Tourism instead of making measurements with water level meters. We collectedsuspended sediment trapped in the sediment samplers once every month or once every few
months. After an absolute drying treatment at 110 °C for 24 hours, we measured theconcentration of particulate caesium-134 and caesium-137 using germanium detectors. The
suspended sediment concentration [g/L] and flow rate [m3/s] were calculated using conversion
formulas created for turbidity and water level respectively (acquiring data every 10 minutes foreach).

Page | 13

Table 3: Catchment area and average caesium-137 inventory in the wide-area river survey
Site

Point NameRiver System

River Name

No.
1
2
3
4

Mizusakai River
Kuchibuto River
Upstream
Kuchibuto River
Midstream
Kuchibuto River
Downstream

Averagecaesium-137
Inventory

Catchment
Area
[km2]

[kBq m−2]

Abukuma River

Kuchibuto River

8

587

Abukuma River

Kuchibuto River

21

408

Abukuma River

Kuchibuto River

63

304

Abukuma River

Kuchibuto River

135

248

5

Fushiguro

Abukuma River

Abukuma River

3645

102

6

Iwanuma

Abukuma River

Abukuma River

5313

96

7

Mano

Mano River

Mano River

76

521

8

Ojimadazeki

Mano River

Mano River

111

418

9

Matsubara

Same River

Same River

871

46

10

OnahamaFujiwara River

Fujiwara River

70

45

11

Tsukidate

Abukuma River

Hirose River

84

222

12

Nihonmatsu

Abukuma River

Abukuma River

2380

88

13

MiyodaAbukuma River

Abukuma River

1287

77

14

Nishikawa

Abukuma River

Shakado River

289

137

15

Kitamachi

Niida River

Mizunashi River

36

537

16

Kawamata

Abukuma River

Hirose River

57

226

17

Marumori

Abukuma River

Abukuma River

4124

113

18

Funaoka Ohashi

Abukuma River

Shiraishi River

775

27

19

SenoueAbukuma River

Surikami River

313

51

20

YagitaAbukuma River

Ara River

185

63

21

Kuroiwa

Abukuma River

Abukuma River

2921

109

22

TomitaAbukuma River

Ouse River

73

117

23

Ota

Ota River

Ota River

50

1638

24

Odaka

Odaka River

Odaka River

50

750

25

Asami

Asami River

Asami River

26

197

26

Tsushima

Ukedo River

Ukedo River

25

813

27

Ukedo

Ukedo River

Ukedo River

153

2329

28

TakaseUkedo River

Takase River

264

696

29

Haramachi

Niida River

Niida River

200

858

30

Akanuma

Abukuma River

Otakine River

243

57

31

Watari

Abukuma River

Abukuma River

5313

96

*The Watari Point (31) is on the bank opposite the Iwanuma Point (6), and was setup as a backup.

14 | Page

1.3. Results(1) Survey in the Hirose River Basin
Figure 3 shows cross-sectional views of the riverbed and photographs taken at the Ochiai
Bridge and Mano Bridge monitoring sites on the Hirose River. The two sites are separated byapproximately 24 km. Although the water depth does not vary appreciably between the twopoints, the river width including the flood channel at Mano Bridge is approximately twice thewidth at Ochiai Bridge, and much sand and gravel is carried by the river and deposited on theflood plain at Mano Bridge.

Figure 3: Photographs and cross-sections of sites in the Hirose River BasinPage | 15

Figure 4 shows the changes in precipitation, daily flux of caesium-137, suspended solids(SS) concentration, and discharge monitored in the Hirose River (Ochiai Bridge) from
September to December 2014. Heavy rains were observed when two typhoons passed Japan in
October 2014. These rains increased the river flow rate considerably, and the concentration of
SS in river water increased simultaneously. The daily flux of caesium-137 was calculated fromthe SS flux and caesium-137 concentration in river water at this time. As a result, thecaesium-137 daily flux was high when the river discharge increased because of the two
typhoons.

Pr. (mm day-1)

0

20
40
60
80

Cs-137 (MBq day-1)

100
600

400

200

0
1200

SS (mg L-1)

1000

800
600
400

200

Discharge (m3 s-1)

0
10
8

6
4
2

2014/12/08

2014/11/19

2014/10/31

2014/10/12

2014/09/23

2014/09/04

0

Figure 4: Changes in precipitation, caesium-137 daily flux, SS concentration, and discharge
at Ochiai Bridge on the Hirose River

16 | Page

Figure 5 shows results for the particulate caesium-137 concentration at monitoring sites inthe Hirose River Basin. The figure presents results of collection and measurement at parts ofeach monitoring site flowing at low-and high speed during the normal stage of water flow on
November 9, 2013, and the results of collection and measurement during a flood on July 23,
2013. In samples taken during the normal stage of water flow, the caesium-137 concentration
was low in both low- and high-velocity zones, falling below minimum detection values (0.05
Bq L−1) at some points. The concentration remained low at both monitoring sites on the Nuno
River and Oguni River (Table 1), which have much caesium-137 deposited upstream. However,the caesium-137 concentration was high at all sites in the Hirose River Basin during floods.

Figure 5: Concentrations of particulate caesium-137 in the Hirose River Basin* below detection limit (0.05 Bq L−1)

Page | 17

Figure 6 shows the measurement results for the caesium-137 concentration in riverbed soil
at various monitoring points in the Hirose River Basin. A comparison of results for 2013 and2014 reveals there was no clear change in trends in the caesium-137 concentration in riverbed
soil. The caesium-137 concentration was higher in both low- and high-velocity zones further
downstream, with low-velocity zones tending to have a higher concentration than high-velocity
zones. The caesium-137 concentration was higher in riverbed soil of the Nuno River and Oguni
River, and in riverbed soil of the Hirose River after these two rivers merge.

Figure 6: Caesium-137 concentration in riverbed soil of the Hirose River Basin

To forecast radionuclide dynamics in the Hirose River with numerical models, we collectednecessary data and established a monitoring network for verification of dynamics forecasting in
the Hirose River Basin. In the 2015 fiscal year, Professor Yasuo Onishi of Washington State
University provided us with the TODAM model to use for model computation in the case of theHirose River, and advice on methods of operation. It will be necessary to conduct a modelcomputation of radionuclide dynamics in the Hirose River Basin by implementing continuous
river monitoring and using the results obtained.

18 | Page

(2) Wide-area survey
In the wide-area survey, sites 1–6 are long-term monitoring sites that have been subject tocontinuous monitoring since June 2011. Changes over time in the particulate caesium-137
concentration [Bq/kg] at these sites are shown in Figure 7. While high values exceeding 10,000
Bq/kg were observed at all sites immediately after the accident, values have tended to decrease
to less than one-tenth of the initial concentrations over 5 years. The rate of decline was highest
in the first year after the accident, and has decreased from the second year onwards.

Figure 7: Temporal change in the particulate caesium-137 concentration at six long-termmonitoring sites
The transition of monthly particulate caesium-137 flux until August 2015 at the same six
long-term monitoring sites is shown in Figure 8. Unlike the case for the caesium-137
concentration, there was no clear declining trend for the caesium-137 flux. This is because thefluctuation ranges of the flow rate and suspended sediment concentration depending on thepresence of floods were far larger than the range of the decrease (one order of magnitude) of theradiocaesium concentration. In addition, the ratio of the integrated value of the particulate
caesium-137 flux relative to the caesium-137 inventory at each point in the basin (i.e.,
caesium-137 inventory multiplied by the catchment area) was 2.7% to 3.4% at two points on the
Abukuma main channel and 0.7% to 1.4% at four points on tributaries of the main channel(Figure 9).

Page | 19

Figure 8: Transition of particulate caesium-137 flux until August 2015 at six long-termmonitoring sites

Figure 9: Cumulative loss of caesium-137 relative to initial deposition in basins after June
2011 at six long-term monitoring sites
The NRA (2015) stated that the difference in the declining rate of the caesium-137
concentration was due to the variation in land use between monitoring sites (source:
Aggregation of data on the distribution and development of migration model for radionuclides
due to the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident infiscal year 2014. Part 2: Survey on radiocaesium transport

in river systems,

http://radioactivity.nsr.go.jp/ja/list/560/list-1.html). Caesium-137 concentrations per initialdeposition in the basin [Bq kg−1/Bq m−2] at sites 1–16 from August 2011 to the end of 2014,
which can be obtained as the caesium-137 concentration divided by the average caesium-137

20 | Page

inventory for each basin, were approximated using the exponential function (y = a exp(−kt))(Figure 10). The rate of decline k [year−1] is plotted with respect to the coverage of land-use
types in Figure 11. The value of k increased with the coverage rates of paddy fields, urban areas,
and farmland.

Figure 10: Caesium-137 concentration per initial deposition in the basin (August 2011 to
the end of 2014). There are differences in the rate of decrease depending on thegeographic point. (NAR, 2015, partially revised)Page | 21

Figure 11: Rate of decrease in the caesium-137 concentration per initial deposition inbasins from August 2011 to the end of 2014 (NAR, 2015, partially revised)

1.4. Conclusion
To forecast radionuclide dynamics in the Hirose River with numerical models, weestablished a collection of necessary data for application of the TODAM model and amonitoring network necessary for verification of dynamics forecasting in the Hirose River
Basin by the 2015 financial year. We also performed a wide-area survey of the Abukuma River
System and major rivers in the Hamadori area. The levels of radiocaesium adsorbed by small
particles in water continuously declined; the rate of decline was affected by the type of land use
in the catchment area.

22 | Page

2. FIP2: Survey of radionuclide movement with wildlife
Summary
To understand the dynamics of radionuclides in the ecosystem of Fukushima Prefecture,
we are studying how radionuclides are assimilated into wild animals, which constitute part ofthe ecosystem. We measured the concentration of radiocaesium in the bodies and food of wild
animals, and analyzed the temporal change and differences among species.
Furthermore, having studied the home range of wild animals because the behavior of wild
animals is closely related to the dynamics of radionuclides in the ecosystem, we found that thehome range of wild boars inside the evacuation zone tended to be larger than that outside theevacuation zone.

2.1. Purpose
The accident at the Fukushima Daiichi Nuclear Power Station caused wide ranging
environmental pollution in the form of radioactive substances. Wild animals living in the naturalenvironment assimilate radioactive substances into their bodies by, for example, eating food. As
a result, radionuclides have been found in the bodies of many wild animals.
In Fukushima Prefecture, we have monitored radionuclides in the muscles of game wild
animals since immediately after the accident in 2011, to ensure the safety and security of theliving environment for hunters and prefectural residents. In the measurement of artificial
gamma-ray emitting nuclides contained in muscle, radionuclides other than caesium-134 andcaesium-137 have been below the detection limit. However, because there is little knowledge
about the movement of radiocaesium from the ecosystem into wild animals, we began a study tounderstand the dynamics of radiocaesium in the ecosystem. It has been speculated that the
behavior of wild animals is closely related to the movement of radiocaesium into wild animals.
However, much remains unknown about the behavior of wild animals, and research on the
behavior of wild animals in areas uninhabited by humans due to evacuation orders isparticularly scarce. We thus studied the behavior of wild animals.

2.2. Implementation Details
Boars were chosen as the main wild animal species for this study, as they are distributed
broadly throughout Fukushima Prefecture, and the caesium-137 concentration in wild boar did
not have an obvious downward trend with time in studies of the accident at the Chernobyl
Nuclear Power Plant. We will eventually expand the study to other wild animal species.
(1) Dynamics of radionuclides in wild animals

Page | 23a) Measurement of the concentration of gamma-ray-emitting nuclides in the bodies of wild
animals
In the measurement of theradionuclide concentration in thebodies of wild animals, wemeasured the concentration of
gamma-ray-emitting

Muscle sample

Measurement of radionuclide
concentration(germanium semiconductor detector)

nuclidescontained in muscle of animals(mainly boar and black bear, wetweight) that were killed throughhunting
following

and
the

pest

control

Figure 1: Measurement of radionuclides inwild animals

procedures

illustrated in Figure 1. In addition, we measured the concentration of gamma-ray-emitting
nuclides in the internal organs of boars using the same procedure to show the distributionof radionuclides in the body.
b) Movement of radionuclides into the bodies of wild animals from the environment
We conducted a composition analysis of the stomach contents of boars to show theirdiet. According to the results of the analysis and the opinions of experts, we sampled thefood of boars in the area around the point that they were captured. We then measured theconcentration of gamma-ray-emitting nuclides in the food samples.
We also examined the potential that boars consume food that naturally contains a highconcentration of gamma-ray-emitting nuclides.
c) Form of radiocaesium contained in stomach contents
The form of radiocaesium is related to the absorption of the radiocaesium from soil
into plants. Similarly, we considered the effect of the form of radiocaesium contained in thestomach contents on the absorption of radiocaesium into the bodies of boars.
(2) Survey of the home range of wild animals
We studied the behavior and home range of boars by attaching a GPS data logger (GPScollar, Figure 2) to each boar’s body. Using GPS points recorded every 15 minutes by the
GPS collar, we investigated the behavior of boars both inside and outside the evacuation area
(Figure 3).

24 | Page

Figure 2: GPS collar

Figure 3: Attaching a GPS collar to a boar that was captured with thehelp of a nuisance animal capture squad and sedated.

2.3. Results(1) Dynamics of radionuclides in wild animalsa) Measurement of the concentration of gamma-ray-emitting nuclides in the bodies of wild
animals
Figure 4 shows the trend of the caesium-137 concentration in boar muscle from May
2011 to December 2015. The figure shows the date the wild boar was captured on the X-axis
and the log-transformed caesium-137 concentration on the Y-axis, with black circles giving
the measurement of each individual. A bar, error bar, and box show the geometric mean,
maximum and minimum values, and the 25% to 75% confidence interval, respectively.

Figure 4: Results of monitoring the caesium-137 concentration in the muscle ofwild boars (fiscal years from May 2011 to December 2015)

Page | 25

Theaverageconcentration

caesium-137

appearstohavedecreased after the 2012 fiscal year.
However,thecaesium-137

concentration

variedappreciably

depending on the characteristics oftheparticular

areas

where

the

measurements

weretaken.

For
Figure 5: Temporal trends of caesium-137 in thecomparison with the case for theboars

capturedinmuscle of boars (Regensberg, Southern

Fukushima

Germany)

Prefecture, we show the case ofRegensburg in southern Germany,

where boars were captured and studied following the Chernobyl Nuclear Accident, in Figure
5 (Semizhon et al., 2009). The caesium-137 concentration varied widely but, similar to thecase for Fukushima Prefecture, there was no clear downward trend. It is necessary to
examine the trend of the caesium-137 concentration in wild boar of Fukushima Prefecture in
the future.
Data

on

the

caesium-137

LegendCs contamination level (Bq/m2)

137

concentration in soil measured by
MEXT from 2011 to 2012 areshown in Figure 6. It is possible
that

the

concentrationofradiocaesium in boar muscle isrelated to the concentration ofradiocaesium in soil. We haveexamined this correlation in detail
by,

for

example,setting

Figure 6: Caesium-137 soil contamination levelprovisional soil contamination levels.

(Fukushima Prefecture)

The caesium-137 concentration in Asian black bear muscle is shown in Figure 7. The
concentration appears to have decreased with time, and the fiscal-year average caesium-137
concentration decreased until the 2014 fiscal year.
We thus confirmed that temporal trends of the caesium-137 concentration varydepending on the species of wild animal. A comparison of the caesium-137 concentrations
contained in various organs of boars, including the muscle, heart, liver, lung, and kidney,shows that the caesium-137 concentration was highest in muscle and that there was a

26 | Page

certaincorrelation in concentrations between muscles and various organs. There was a small
number of samples and greater scrutiny will thus be needed in the future, but we expect thisstudy will contribute to showing the distribution of caesium-137 in the boar body and theradiocaesium concentration in the whole boar body.

Figure 7: Results of monitoring the caesium-137 concentration in the muscle of
Asian black bear (fiscal years from May 2011 to December 2015)b) Movement of radionuclides into the bodies of wild animals from the environment
Havingcomposition

conducted
analysis

of

a
the

stomach contents of boars, wefound that the contents can beroughly divided into four categories
depending on the season: January
to March, April to June, July to
September,

andOctobertoFigure 8: Compositional analysis of stomach
contents; stomach contents are sieved
and analyzed under a microscope

December. It is believed that thecomposition of the food eaten by boars changes with the seasons. In any season, vegetable
matter was most common food and animal matter accounted for at most a few percent of thefood. In the future, we will investigate the seasonal changes in the concentration ofradiocaesium in the stomach contents, and the correlation of the concentrations ofradiocaesium in the muscles and stomach contents.

Page | 27

In Europe, the cause of the high concentration of radiocaesium in boar muscle wasbelieved to be the fungus tsuchidango (deer truffle). In the composition analysis of stomach
contents, we could not find any pieces of fungi. Additionally, we should be able to see aseasonal fluctuation of the caesium-137 concentration if fungi were the cause of the highcaesium-137 concentration in the muscle of the boars, but to date, no such trend has been
seen in Fukushima Prefecture. We will continue the investigation of the relationship between
fungi and the caesium-137 concentration in the bodies of wild boars.
c) Formofradiocaesium

containedin

Ion exchange form

stomach contents
Caesium in soil has three forms (Figure

Organic binding formaaa
Soil

Particle binding formaaa

9). The ion exchange form is mainly absorbedby plants while the particle binding form

Figure 9: State of caesium in soil

coupled with clay minerals is difficult to absorb. It is thought that boars eat soil together withfood when consuming subterranean food, or that they eat soil intentionally to obtain minerals,
and there is thus the potential for caesium-137 in soil to be absorbed into the body. We arecontinuing surveys to show that soil consumption and the form of radiocaesium in the soil
are responsible for the caesium-137 concentration in muscle being higher in boars than inother wild animals.
(2) Survey on the home range of wild animals
Although boars have a stable home range like that illustrated in Figure 10, there are nodata of details such as the shape, area, and internal structure of the home range. In a survey
on the home range of boars, we were able to divide the home range into residential zones
with a high point density (areas including nearly 95% of GPS points according to density
analysis) and a roaming zone (minimum convex polygon) in which all GPS points were
included, as shown in Figure 11. In this case, the analysis shows that the boars had two
residential zones, the total area of which was approximately 37 ha, and that the boars had atotal home range of 244 ha.

28 | Page

Residentialzone

Residential
Roaming

Residential Zone A

zone

Residential Zone B

zone
Residentialzone
Residential

Roamingzone

2.2 kmzone

2 km

Figure 10: Structural diagram of a

Figure 11: Structure of the actual home range

home range
Taking the analysis further, there were areas within residential zones where GPS points
were clustered densely, which we have labeled as the residential core (Figure 12). The areaof the residential core was very small, being only 3.3 ha in this case.

Residential
Core

Figure 12: Residential corea) Home range of boars outside the evacuation area
Outside the evacuation area, we surveyed the boar home range in Fukushima City,
located in a peri-urban area, and Tazawa in Nihonmatsu Iwashiro District, located in a
mountainous area. Results are presented on the same scale in Figure 13 (with a 1 km2 mesh).

No. 52, Fukushima City (♂)

No. 58, Fukushima City (♂)

No. 66, Nihonmatsu City (♀)

No. 67, Nihonmatsu City (♀)

Residential zone: 37 ha

Residential zone: 41 ha

Residential zone: 51 ha

Residential zone: 20 ha

Home range: 244 ha

Home range: 186 ha

Home range: 207 ha

Home range: 97 ha

Figure 13: Size of boar home range outside the evacuation area

Page | 29

Although individual differences can be seen, the residential zone where the boars spend
most of their lives was just 20 to 50 ha. The roaming zone was only 100 to 250 ha,
suggesting that boars are the type of animal that settles in one region.
b) Home range of boars inside the evacuation area
To investigate what constitutes the home range of boars when human activity has
declined, we surveyed the home range of boars in Tomioka Town, which has been designatedan evacuation zone. Figure 14 shows the results of the home range survey conducted in
Tomioka Town in 2014. Evacuation zones in the figure were classified on August 8, 2013.
The mesh scale is 1 km2.
Results for boar 50 were obtained during a survey conducted by the Ministry of theEnvironment in the 2013 fiscal year as reference data. Decontamination activities were notconducted in the 2013 fiscal year, and furthermore, there had been a lack of human activity
for more than 2 years since the evacuation. The areas of the residential zone and home range
were both 5 to 6 times those in Fukushima or Nihonmatsu City, and it is thus considered thatthe home range tends to expand in an environment where there is less pressure from humans.

Joban

Route No. 6

Expressway

No. 85

No. 208

No. 50Figure 14: Home range and land use in Tomioka Town
Boar 85 was mounted with a collar in September 2014. Around that time,
decontamination activities for restricted-residence areas began in Tomioka Town, and Figure
15 shows the effect of these activities on the home range. As described by the legend, themean center of the home range is shown for three periods of one month each following

30 | Page

collaring. Perhaps owing to the effect of decontamination pressure, we find that the center ofthe home range moved from Tomioka Town to Okuma Town.

Okuma

Legend1 month after collaring

Tomioka

2 months after collaring
3 months after collaring
Decontamination Pressure

Movement distance of mean center from period 1 to period 3 was 2.3 km)

Figure 15: Home range and mean center of movement of boar 85
Figure 16 shows the home range ofboar 208, to which a collar was attachedon October 2014. The area of boar 208
was only one-third that of boar 85. During

Legend1 month after collaring
2 months after collaring

the collaring period, decontamination was
3 months after collaring

underway in most of the home range, andperhaps because of the decontamination

Decontamination Pressurepressure acting from all four sides of thehome range, the mean center of movement
hardly moved at all during the third

Figure 16: Home range and mean center ofmovement of boar 208

period.
From the results of these surveys, it is considered that the size of the home range wasaffected by human activity or environmental factors. Figure 17 shows the areas of theresidential zones and home ranges of boars captured both inside and outside the evacuation
area. Boar 50 was under no pressure from people or decontamination. The home range ofboar 85 expanded to Okuma Town owing to decontamination pressure. Boar 208 was under
decontamination pressure from all four sides in the restricted-residence area. Boars 52 and58 were in a peri-urban environment. Boars 66 and 67 were speculated to be affected bydamage control pressure in a mountainous region. It seems that the size of the home range
decreased with an increase in human pressure.

Page | 31

(ha)
2,000
1,556
1,500
1,070
Home Range
行動圏

1,000
500

240

327

定住域
Residential zone

511
105

244
37

186

41

207

51

97 20

No66

No67

0
No50

No85

No208

No52

No58

Pressure

Figure 17: Area comparison of the home range and residential zone

Table 1: Sample listIDsexweight(kg)GPS collar attached dates(day)

No.50
♂
37
81

No.85
No.208
♀
♀
48
51
99
117

No.52
♂
44
99

No.58
♂
70
50

No.66
♀
35
110

No.67
♀
37
34

The number of collared samples was small, and the sex, body weight, and duration that thecollar was worn was different for each collared sample (Table 1). The size of the home range
was affected by various factors, such as the sex and growth stage of the boar and the durationof GPS data. We therefore cannot provide concrete conclusions at this stage, but it isconsidered that the home range tended to shrink with increased human pressure.

32 | Page

3. FIP3: Project for studying decontamination technology for rivers
and lakes
Summary
The third FIP organized knowledge on the behavior of and countermeasures forradionuclides (i.e., radiocaesium) in rivers and lakes. In rivers, where examples ofcountermeasure implementation were limited, a decontamination method was devised andtested and its effectiveness was confirmed. Additionally, the state of pollution wasinvestigated in riverside parks and countermeasures were considered.

3.1. Purpose
The diffusion of radionuclides (especially radiocaesium) into the environment due to the
Fukushima Daiichi Nuclear Power Plant accident has caused failures and anxiety in the use andmanagement of rivers and lakes. For this reason, radionuclides in water, sediment, and aquatic
products have been monitored and their behavior has been investigated mainly by thegovernment and research institutions; countermeasures are currently being implemented. In thethird FIP, radiocaesium countermeasures applicable to Fukushima Prefecture were organizedusing global knowledge, and a decontamination test was conducted because case examples of
reducing external radiation exposure were limited for rivers in the prefecture. Additionally, thestate of pollution was investigated in areas of public use (i.e., waterside parks) along other rivers,
and the countermeasures were devised.

3.2. Details of Implementation(1) Organization of knowledge on radiocaesium countermeasures in rivers and lakes
By referencing guidelines published by relevant ministries (MOE, 2014; MAFF, 2015) andthe experience of the Chernobyl Nuclear Accident (IAEA, 2006), problems and possible
countermeasures relating to the use of rivers and lakes in Fukushima Prefecture are organized inTable 1.
(2) Experimental test of radiocaesium decontamination in a rivera) Purpose
Among the problems raised in Table 1, the case examples of external exposure
countermeasures in rivers are limited particularly for decontamination. A river is a majortransport pathway for radiocaesium on land, and sediment containing radiocaesium issometimes thickly deposited on floodplains. In general, only the top few centimeters of soil inPage | 33

Fukushima Prefecture were decontaminated owing to radiocaesium accumulating only in thatlayer in farmland, forest, and residential areas. However, it is not clear whether this method isapplicable to floodplains. We therefore tested the removal of topsoil on a floodplain as adecontamination method according to the depth distribution of radiocaesium.

Table 1: Problems and possible countermeasures for the use of rivers and lakes
ProblemRelated media

Possible countermeasures

Internal exposure via drinking waterRivers and lakes

Change to alternative drinking water sources

Transfer of radiocaesium fromRivers and lakes

Mitigation of sediment inflow using silt fences, use of

irrigation water to crops andthe sedimentation function of a dam

external exposure during farm

Irrigation ponds

Silt fences, decontamination of bottom sedimentwork

Overall

Potassium fertilization of farmland

Internal exposure via the ingestion

Rivers and lakes

Restriction of the distribution and input of potassiumof aquatic products
External exposure when using(limited to closed lakes)
RiversAccess control, decontamination of floodplains,waterside areas (e.g., parks, roads,

mitigation of deposition onto floodplains by promoting

and housing)deposition onto riverbeds through riverbed excavation

Common to all problems

Lakes

Access control

Irrigation ponds when

Access control, decontamination of bottom sediment,

being drained

covering with sandSediment transportation prevention and decontamination of source areas ofsediment. Risk communication for anxiety resulting from lack of information
communicationb) Method
The test site was located at the most downstream position of the Kami-Oguni River, athird-order tributary of the Abukuma River, at a distance of 55 km northwest of the
Fukushima Daiichi Nuclear Power Plant. The test section had a length of 170 m and an
average width between banks of 15 m and a river channel width of 2 to 6 m under baseflow
conditions (Figure 1). The left bank is used for an elementary school and its school road, andthe right bank is used for an orchard. The floodplain is used for classes at the elementary
school. The elementary school and the school road had been decontaminated before thepresent test.

34 | Page

The test was conducted according to the process outlined in Figure 2. Eighteen laterallines were set at intervals of 10 m in the direction of the river flow (Figure 3), and the air dose
rate 1 m above the ground on the lateral lines was measured using NaI scintillation survey
meters without collimation. The measurement was conducted before decontamination, at thecompletion of decontamination, and 3 and 6 months after decontamination. Before
decontamination and 6 months after decontamination, sediment was sampled from sevenpoints on each of the floodplain and riverbed (Figure 3) and then subjected to radionuclide
analysis using Ge semiconductor detectors. Sampled sediment was classified using sieves
after the analysis, and the percentage weight of the mud fraction (i.e., silt and clay) relative tothe total weight was then calculated. The water level was continuously monitored upstream of
the test section.
The annual additional external exposure dose before and after decontamination was
calculated as follows. The staying time was assumed to be 10 minutes per day for the schoolroad on the left bank (35 hours per year) and 2 hours per week for the floodplain (100 hours
per year). These values were multiplied by the average air dose rate after deducting thebackground value (0.04 µSv/h).

(GSI Map)

Elementary
SchoolSchool road

Deposition density ofradiocaesium(Nuclear Regulation Authority)

Figure 1: Study site outline

Decontamination Range(excluding the riverbed)

OrchardPage | 35

Figure 2: Examination process(GSI map)

Air dose rate
Sediment on the floodplain
Sediment on the riverbed
Water level

Figure 3: Measurement pointsc) Results and discussion
The vertical distribution of the activity concentration of radiocaesium on the floodplainis shown in Figure 4. Along lines 4, 6, and 8, the concentration exceeded 10,000 Bq/kg(caesium-137) to a depth of 15 cm. In the layers corresponding to that depth, the percentage
mud fraction was high at 31% to 55% (Figure 4). Because radiocaesium has the nature ofbeing strongly adsorbed to clay and silt (He and Walling, 1996), it is unlikely that

36 | Page

radiocaesium penetrated below a depth of 10 cm at points with a high percentage of the mud
fraction. Along lines 10 and 14, the concentration peaks were distributed below a depth of 10
cm with a low percentage of the mud fraction of 2% to 17%. However, it is unlikely thatcaesium-137 penetrated below a depth of 10 cm sufficiently to form the layers with aconcentration exceeding 5000 Bq/kg. Therefore, those surface sediments were probably
deposited during floods after the initial deposition of radiocaesium. In consideration of thevertical distribution, we set a removal depth of 15 to 35 cm on the floodplain. A similar
vertical distribution of radiocaesium has been reported on floodplains (Tanaka et al., 2015;
Konoplev et al., 2016), indicating that the investigation of the vertical distribution in advanceof decontamination is important.
The vertical distribution of radiocaesium activity concentration on the riverbed is shownin Figure 5. In contrast to the distribution for the floodplain, the distribution for the riverbed
was nearly uniform. Relatively low values of the radiocaesium activity concentration andpercentage of the mud fraction were observed, with 70% of samples having a concentration
lower than 1000 Bq/kg and a mud fraction lower than 5%. Mikami et al. (2014) also reported
a difference in distributions between a floodplain and riverbed for a river 4 km to the east of
the test site, and indicated two factors responsible for the difference. One factor is that mudwith a high radiocaesium concentration tends to be easily discharged on a riverbed under
running water. The other is the promotion of sedimentation on floodplains by the plantcommunity, which acts as an obstacle to the flow of water and suspended solids during floods.
In consideration that river water provides a shield against gamma rays emitted from theriverbed, we did not decontaminate the riverbed in this test.

Page | 37

Lateralline 2Lateralline 4Lateralline 6Lateralline 14

Lateralline 18

Lateralline 8Percentage of mud
fraction

Lateralline 10Figure 4: Vertical distribution of the activity concentration of radiocaesium infloodplain sediment before decontamination

The distribution of the air dose rates 1 m above the ground is shown in Figure 6. The
average value and standard deviation were 0.66 ± 0.22 µSv/h before decontamination but
decreased by half to 0.34 ± 0.11 µSv/h after decontamination, confirming the effectiveness ofthe test method. There was hardly any change in the value of 0.34 ± 0.12 µSv/h three months
after decontamination. Afterward, although there was a flood in March 2015, the activity
concentration of caesium-137 remained low in sediment at a depth of 0 to 20 cm on thefloodplain (860 ± 760 Bq/kg) and in sediment at a depth of 0 to 5 cm on the riverbed (660 ±720 Bq/kg). As a result, the air dose rate six months after decontamination (0.30 ± 0.12
µSv/h) was hardly different from that at the completion of decontamination. The effects ofdecontamination have therefore been maintained.

38 | Page

Lateralline 8Lateralline 2Lateralline 4Lateralline 6Lateralline 10Lateralline 14

Lateralline 18

Percentage of mud
fraction

Figure 5: Vertical distribution of the activity concentration of radiocaesium in riverbed
sediment before decontamination

Air dose rate(µSv/h)Before decontamination(August 2014)

Completion of decontamination(November 2014)

Three months after decontamination(February 2015)

Six months after decontamination(May 2015)

Figure 6: Temporal change in the air dose rate

Page | 39

Annual additional external exposure doses for using the school road and floodplain were
estimated to be 0.089 mSv/year before decontamination and 0.034 mSv/year after
decontamination, resulting in 62% reduction of the exposure dose. In the town where the test
was conducted, an average exposure dose of 1.23 mSv/year was obtained for the period from
July 2013 to June 2014 using a glass dosimeter (Date City, 2015). The use of the test site
corresponded to 7.2% of the exposure dose in daily life before decontamination and 2.7%
after decontamination. Therefore, reduction of the exposure dose by decontamination was
estimated to be 4.5% of the exposure dose in daily life.
(3) State of pollution in river parks and examination of countermeasure methodsa) Purpose
As stated in section (2), radiocaesium sometimes accumulates along with sedimentdeposition on riversides. Because upstream areas are appreciably polluted in the coastal
region of eastern Fukushima Prefecture, there is concern about the possibility that thefloodplains in the downstream area are more contaminated than the surrounding area.
Riverside parks are one type of floodplain area used by people. We therefore investigated thestate of pollution and the effect of floods on riverside parks in the coastal region, anddiscussed countermeasures.
b) Method
Study sites were located at two points downstream of the Niida River, one of the majorrivers in the coastal region (Figure 7). Park A is located along the main stream of the Niida
River, while Park B is located along the Mizunashi River, a first-order tributary of the Niida
River. A dam is located 5 km upstream from park B. Parks A and B have areas of 2.7 and 1.6
ha, respectively. In August 2015 before a flood and in September 2015 after the flood, the air
dose rate was measured 5 cm and 1 m above the ground using a portable gamma-ray
measuring device (Gamma Plotter H, Japan Radiation Engineering Co., Ltd.). At the sametime, the additional external exposure dose was measured using a dosimeter (Dose e nano,
Fuji Electric) for various activities, including recreation, walks, and park maintenance.

40 | Page

Park A

Niida River
Takanokura Dam

Deposition densityof radiocaesiumPark B(Nuclear Regulation Authority)

Nuclearplant

Figure 7: Location map of study sitesc) Results and Discussion
The distribution of the air dose rate in park A during August and September 2015 isshown in Figure 8. In August 2015, the air dose rate was 0.20–2.14 µSv/h at a height of 5 cm
and 0.22–1.75 µSv/h at a height of 1 m. Relatively high values exceeding 1.0 µSv/h were
distributed primarily in the northeastern part of the park along the river, suggesting theaccumulation of radiocaesium by sediment deposition. However, after a flood in September
2015, the values fell below 1.0 µSv/h at many points on the riverside and in the northeasternpart of the park. This is likely attributed to the deposition of a large quantity of coarse
particles (mainly sand) along the river and erosion up to several tens of centimeters in thenortheastern part of the park. The appreciable deposition and erosion were caused by theextreme flood (resulting from 385 mm precipitation over 6 days recorded at a weather station
7 km to the southeast).
For the additional external exposure dose, the value of use situations before the flood
was 0.092 mSv/year under the assumption of a staying time of 180 hours per year, while after
the flood, it fell 30% to 0.064 mSv/year. In this city where park A was located, an average
exposure dose of 0.44 mSv/year has been measured using a glass dosimeter in the period
from July to September 2015 (Minami-Soma City, 2016). The use of park A corresponded to
21% of the exposure dose in daily life before the flood and 15% after the flood. In
considering countermeasures for park A, it is noted that although the high air dose rate wasstill distributed along the river after the flood, the utilization of the area along the river seems
to be limited by the lush reed community along the river. Moreover, as described above, theexposure dose was estimated to be less than 0.1 mSv/year. We therefore conclude that there islittle to fear under present conditions. Meanwhile, there is the possibility of recontamination
by radioactivity sediment on the floodplain in the future. Monitoring and future prediction are
effective responses to such concerns.
The distribution of the air dose rate in park B during August and September 2015 isPage | 41

shown in Figure 9. In August 2015, the air dose rate was 0.18–1.06 µSv/h at a height of 5 cm
and 0.23–0.69 µSv/h at a height of 1 m, except for the residential area to the south of the park.
In contrast to the distribution in park A, the distribution in park B was nearly uniform, and theair dose rate along the river was not high. In the extreme flood of September 2015, thenorthern half of park B appeared to be inundated according to the distribution of plant residue
washed down, but sediment and erosion were rarely found. As a result, there was almost nochange in the air dose rate even after the flood. Similarly, for the additional external exposure
dose, the value of use situations hardly changed from 0.047 mSv/year before the flood to
0.046 mSv/year after the flood (assuming a staying time of 190 hours per year). It is inferredthat one factor responsible for the small change was the capture of suspended solids by thedam upstream of park B. Considering the low exposure dose and weak effect of floods, weconclude that there is little to fear under the present conditions also in park B.

42 | Page

Downstream

Downstream

Upstream

Upstream

August 2015 (height of 5 cm)

August 2015 (height of 1 m)

Downstream

Downstream

Upstream

Upstream
September 2015 (height of 5 cm)

September 2015 (height of 1 m)

Figure 8: Distribution of the air dose rate in park A. The white broken line represents thepark area.

Upstream

Downstream

Downstream

August 2015 (height of 1 m)

August 2015 (height of 5 cm)

Upstream

Upstream

Downstream

September 2015 (height of 5 cm)

Upstream

Downstream

September 2015 (height of 1 m)

Figure 9: Distribution of the air dose rate in park B. The white broken line represents thepark area.

Page | 43

References
Date City (2015) Date Recovery/Rejuvenation News (No. 22).
http://www.city.date.fukushima.jp/soshiki/12/763.html. (in Japanese)
He Q., Walling D. E. (1996) Interpreting particle size effects in the adsorption of 137Cs andunsupported 210Pb by mineral soils and sediments. Journal of Environmental Radioactivity,
30, 117-137.
IAEA (2006) Environmental consequences of the Chernobyl accident and their remediation:
Twenty years of experience report of the Chernobyl forum expert group ‘environment’.
Vienna.
MOE (2014) Guidelines for Decontamination. https://josen.env.go.jp/material/. (in Japanese)
Konoplev, A., Golosov, V., Laptev, G., Nanba, K., Onda, Y., Takase, T., Wakiyama Y.,
Yoshimura, K. (2016) Behavior of accidentally released radiocaesium in soil–water
environment: Looking at Fukushima from a Chernobyl perspective. Journal ofenvironmental radioactivity, 151, 568-578.
Mikami, T., Maie, N., Shimada, H., Kakizaki, T., Takamatsu, R., Itou, N., Tanaka, K., Shima, E.
(2014) Influence of microtopography on radioactive caesium accumulation in waterside
lands: Case study of second order tributaries of the Abukuma River flowing throughFukushima Prefecture. Society on Water Environment Journal, 37 (6), 259-264. (inJapanese)
Minamisoma City (2016) 2015 No. 2 individual cumulative dose measurement (7/2015 –9/2015) results. Cityhttp://www.city.minamisoma.lg.jp/index.cfm/10,28438,61,367,html.
(in Japanese)
MAFF (2015) Technical Manual on Countermeasures for Radioactive Material in Ponds.
http://www.maff.go.jp/j/nousin/saigai/tamemanu_zentai.html. (in Japanese)
Tanaka, K., Kondo, H., Sakaguchi, A., Takahashi, Y. (2015) Cumulative history recorded in thedepth distribution of radiocaesium in sediments deposited on a sandbar. Journal ofEnvironmental Radioactivity, 150, 213-219.

44 | Page

4. FIP4: Development of environmental mapping technology with GPS
walking surveys
Summary
Fukushima Prefecture developed environmental mapping technology with GPS walking
surveys as a tool for surveying the regional distribution of air dose rates.
This report covers the results of parameter verification necessary for the development of
this technology and the history of development.

4.1. Purpose
To grasp the air dose rate (hereinafter simply referred to as the dose rate) in Fukushima
Prefecture after the accident at the Fukushima Daiichi Nuclear Power Plant, we have conducted
fixed-point measurements with monitoring posts and dose rate measurements in car-borne
surveys using the GPS-linked dose rate measurement device KURAMA (Kyoto University
RAdiation MApping System), and have provided information to prefecture residents on theprefecture homepage (Image 1, Figure 1).

(a)Image 1: Example of monitoring currently being conducted(a): Example of a fixed-point measurement(using a real-time dose-rate measurement system)(b): Example of a car-borne survey(KURAMA-II installed on the back of a local bus)(b)

Page | 45

(a)

(b)

Figure 1: Radioactivity measurement in Fukushima Prefecture(http://fukushima-radioactivity.jp/pc/)(a): Example of a fixed-point measurement(b): Example of a traveling survey
As of March 2016, measurements are being made at 3500 fixed points with monitoring
posts in Fukushima Prefecture. Car-borne surveys using local buses are also being conductedwith the purpose of interpolating the fixed-point measurements.
It is, however, difficult to conduct fixed-point measurements or car-borne surveys in someplaces, including parks, forests, and alleys near residential areas, and dose rates sometimes
differ between fixed measuring points at the same facility or site (Figure 2). For these reasons,in addition to fixed-point measurements and car-borne surveys, we require measurement
technology with which to grasp a more detailed distribution of dose rates, and we need topresent the measurement results in a format that is easy to understand.
Therefore, to employ interpolation to obtain dose rates for parks, forests, and alleys nearresidential areas where fixed-point measurements and car-borne surveys are difficult, wedeveloped environmental mapping technology using GPS walking surveys together withunmanned aerial vehicles (UAVs) developed by the IAEA.
The prefecture and IAEA have shared the development of environmental mapping
technology with GPS walking surveys (FIP4) and environmental mapping technology withunmanned aerial vehicles (FCP3), and by combining these technologies and visualizing
measurement results, we were able to create dose distribution maps that are more detailed andeffective.

46 | Page

Survey meter

Monitoring post, etc.

Car-borne survey

Range where the dose rate can be obtained with car-borne surveys and fixed-point measurements
Range of walking surveys

Figure 2: Measurement ranges of conventional measurement methods

4.2. Implementation Details(1) Development of equipment
We used the KURAMA-II, which was developed by Kyoto University, for walking
surveys, and assembled five pieces of equipment in a way suited to walking surveys (Image 2).
The orange backpack contains a CsI (T1) scintillation detector, which is a low-dose-rate
detector, and a high-precision GPS unit.

(a)

(b)

Image 2: Walking survey equipment(a): Appearance of the devices(b): Low-dose-rate CsI detector (Hamamatsu Photonics K.K. C12137-01) andhigh-precision GPS unit (SOKKIA GIR1600)

Page | 47

The measurement screen is shownin Figure 3. The measurement interval
may be selected as 3 seconds, 5 seconds,
and so on. At the start of themeasurement, information such as thecurrent position and dose rate arerecorded to a notebook computer, andthe position information, dose rate,
trends,andmapping

resultsaredisplayed on the computer screen.

Figure 3: Display screen on a personal computer

Measurers can look at the screen to check the measurement position and dose rate while
conducting detailed measurements.
(2) Development of mapping technology using geographic information systems (GISs)
We conducted a specification study and developed a GIS tool for capturing, combining,and mapping the dose rate and position information gained from walking surveys and UAVs.
An overview of the tool is shown in Figure 4.

Result of air-borne
survey by a UAVResult of walking
surveyGIS tool

Combined map

Figure 4: Overview of the GIS tool

Figure 5: Data including the dose rate

It is possible to produce a contour map

using the GIS tool. Data incomma-separated-value format recorded in walking surveys are converted to Microsoft Excel
file format (Figure 5), and point data with dose rate information are created from the latitudinaland longitudinal information contained in the data (Figure 6). With the GIS tool, it is possible
to estimate the dose rate at unmeasured positions and to produce contour maps from the point
data created using any interpolation algorithm, such as a Kriging or IDW algorithm (Figure 7).

48 | Page

Figure 6: Map data and dose plot

Figure 7: Interpolated dose map

The tool was made with the purpose of combining and mapping walking survey data and
UAV data. However, because a method of evaluating aerial surveys with UAVs has yet to be
determined, we will reexamine this purpose after the development of the UAV is complete.
(3) Gathering parameters necessary for walking surveys
We conducted a field test of walking
surveys, and gathered data for evaluation andanalysis (Picture 3). Data were gathered to
check

the

direction

characteristics

andappropriate measurement density, as well as
to determine correction factors.
a) Checking direction characteristics
Shielding

from

the

measurers

themselves affects the contribution from theradiation source depending on the walking

Picture 3: View of a walking survey

direction in walking surveys (Figure 8). Walking surveys were therefore conducted bychanging the walking speed and by walking back and forth so as to straddle the radiation
source and check the effect of direction characteristics.
As a result, while shifts occurred in places where peaks appeared, they fell within arange of about 2 meters, and measurements showed that the maximum value of the dose rate
was nearly the same during forward and reverse passes (Figure 9). We also confirmed that
reducing the walking speed caused the peaks of the dose rate distribution to grow sharply(Figures 10 and 11).

According to the above results, we consider the effect of direction characteristics
on walking survey measurements made at a constant walking speed to be weak.

Page | 49

Not shielded

Shielded

Figure 8: Measurement of direction Figure 9: Measurements after changing speed andcharacteristics

Figure 10: Change in walking speed

direction

Figure 11: Change in measurements due towalking speedb) Determination of correction factors in a comparison test with survey meters
We assumed measurements made with a NaI(Tl) scintillation survey meter (TCS-172B)
at a height of 1 m to be the most reliable, and the survey meter was calibrated withtraceability. We compared measurements made using a survey meter with those obtained in awalking survey (Image 4). A comparison was made at several points with differing dose rates.
At each point, we faced north, south, east, and west and made measurements five times ineach direction to mitigate direction characteristics. We then took the average value for all
directions as the measurement for that point. We next plotted the measurements of walking
surveys against the survey meter to determine the correction factor.

50 | Page

(a)

(b)

Image 4: Images of measuring(a): Measurement with a survey meter(b): Measurement in a walking survey
Both measurements were made facing four directions
The results of the comparison are shown in Figure 12. There was good linearity between
the measurements of walking surveys and the survey meter below a survey metermeasurement of 1 μSv/h, whereas the linearity deteriorated above approximately 1 μSv/h.
This phenomenon is due to count loss caused by excessive radiation incidence on the CsI
detector.

Page | 51

1.0

NaI(Tl) Scintillation Survey meter /μSv·h-1(a)y = 1.3287x
R² = 0.9957

0.8
0.6
0.4

y = 0.9888x
R² = 0.9931

0.2
0.0
0.0

0.2

0.4

0.6

0.8

1.0

Walking Survey / μSv·h-1

NaI(Tl) Scintillation Survey meter /μSv·h-1

20(b)

y = 0.2553x2 + 1.0814x
R² = 0.9963

15

10
y = 1.1285x
R² = 0.9984

5

0
0

5

10

15

20

Walking Survey / μSv·h-1

Figure 12: Comparison of measurements of the survey meter and walking survey(a): Chart plotting data below 1 μSv/h(b): Chart plotting all data
● Comparison of the measurements of the low-dose-rate CsI detector and NaI survey meter● Comparison of the measurements of the high-dose-rate CsI detector and NaI survey meter
Note that the approximate curve is not affected by the self-dose from the measurement detector,
with the intercept being zero.

52 | Page

Image 5: High-dose-rate CsI detector(Hamamatsu Photonics K.K. C12137)
In light of the above results, we changed the detector to a high-dose-rate CsI detector(Image 5) and compared the results obtained using the survey meter with measurement resultsof walking surveys again. The results are shown in Figure 12(b). We confirmed that as aresult of changing the detector, the linearity of walking survey measurements against survey
meter measurements is obtained even in the high dose range. We also confirmed that thehigh-dose CsI detector can make better measurements than the low-dose rate CsI detector in
the high dose range in field tests. This is also confirmed in Figure 13, which shows thewalking survey results having changed detectors at the same geographic point. The maximum
indicated value is higher for the high-dose-rate CsI detector than for the low-dose-rate CsI
detector, and the high-dose-rate area represented by red markers appears, indicating thatmeasurements are made without counting loss of radiation.
According to the above comparisons, we set the correction factor of walking surveys to
1.3 when using the low-dose-rate CsI detector at points with a dose rate less than 1 µSv/h and1.1 when using the high-dose-rate CsI detector.

Page | 53

Level μSv/h

Level μSv/h

(a)

(b)

Figure 13: Walking surveys having changed the detector(a): Walking survey with the low-dose-rate CsI detector
The indicated value range is 2.77 to 5.99 μSv/h.
(b): Walking survey with the high-dose-rate CsI detector
The indicated value range is 5.00 to 29.5 μSv/h.
c) Confirming variations in measurements
We conducted-fixed point
0.14

variations in measurements for a

0.12

to

measurement time of 3 seconds
in the low dose rate range.
Fixed-point measurements weremade with both the low-dose-rate
CsI

detectorandthehigh-dose-rate CsI detector.
Results showed that the

Walking Survwy / μSv·h-1

confirm

measurements

KURAMA for
low dose rate
KURAMA forhigh dose rate

0.10
0.08
0.06
0.04
0.02
0.00
3

33

63
time / sec.

93

123

variation in measurement results
was larger for the high-dose-rate

Figure 14: Confirming variations in measurements

CsI detector at points with a low
dose rate (Figure 14). The variation coefficient obtained from dividing the standard deviationof measurements by the average value was 19.7% for the low-dose-rate CsI detector but
42.7% for the high-dose-rate detector. Error in measurements made with the low-dose-rate
detector was small because of the high counting rate achieved with the large crystal whileerror in measurements made with the high-dose-rate detector was large because of the small

54 | Page

counting rate achieved with the small crystal.
On this basis, we decided to use the low-dose-rate CsI detector, which has a small
variation at low dose rates, at geographic points with a dose rate less than 1 µSv/h, and to use
the high-dose-rate CsI detector at geographic points with a dose rate greater than 1 µSv/h.
(4) Conducting walking surveys
With the purpose of studying the operation of walking surveys and acquiring basic data,
we conducted walking surveys at places with differing conditions. Examples of such walking
surveys are described below.
a) Walking survey in western Fukushima City
We conducted a walking survey on a trial basis in western Fukushima City. At the centerof this geographic area is a surface paved with asphalt, with ditches along the edges. There
were no obstructions on the outside of the asphalt surface, leaving the surface wide open andsurrounded by grass. Results of a walking survey conducted at this geographic point are
shown in Figure 15. The paved surface at the center of the range of the walking survey had alow dose rate compared with that of the surroundings. It is considered that this low dose rateis due to the easy decontamination of the paved surface and the strong effect of weathering. In
addition, the radiation dose in the vicinity of the ditch was higher than that of thesurroundings. This is probably because there was an inflow of radioactive material from thesurrounding area. We conducted a high-density walking survey and tested interpolation with a
GIS tool (Figure 16). Interpolation was conducted with IDW. The interpolated radiation dose
rate in the paved area was low, and the dose rate in the vicinity of the ditch was high.
Level μSv/h

Paved area

Figure 15: Results of a walking survey inwestern Fukushima City

Level μSv/h

Figure 16: Results of interpolation with IDWPage | 55b) Walking survey in the periphery of a temporary storage area
We conducted a walking
Level μSv/hsurvey in a temporary storage area
and its periphery in the Nakadori
region of Fukushima Prefecture(Figure 17). The area inside the redframe in the figure is the temporarystorage area. The dose rate near the
temporary storage area was equal toor less than the dose rate in the
periphery,

and

no

effectofdecontamination on the outside area
was seen in this temporary storage
Figure 17: Dose map (with the temporary storage

area.

area indicated by the red frame)c) Walking survey in the Hamadori region (outside the evacuation zone)
We conducted a walking survey around rivers in the Hamadori region of Fukushima
Prefecture (outside the evacuation zone) (Figures 18 and 19). There is a paved surface on theleft side of the figure, with the rest of the study area being gravel or grassland. The dose rate
was low on the paved surface and nearly uniform in other areas.
Level μSv/h

Level μSv/h

Figure 18: Dose map

Figure 19: Results of interpolation by IDWd) Walking survey in a difficult-to-return evacuation zone
We conducted a walking survey in a difficult-to-return evacuation zone in Fukushima
Prefecture (Figures 20 and 21). The area where the walking survey was conducted was nearly
uniform grassland. The dose rate was nearly uniform in the area, with no large deviation
observed.

56 | Page

Level μSv/h

Level μSv/h

Figure 20: Dose map

Figure 21: Results of interpolation with IDW(5) Manual Production
We published a manual summarizing how to conduct walking surveys. The
manual is written with a combination of pictures and text to be easily understood.
4.3. Summary
Results were obtained in developing walking surveys by 2015.
In terms of developed equipment, the walking survey system adopted KURAMA, which
was designed by Kyoto University and has a structure suitable for a walking survey.
Additionally, to analyze the obtained data or to work with other monitoring methods, such as a
UAV survey, we prepared a GIS data processing system. Furthermore, by collecting data for thedetermination of direction characteristics and calibration constants, it has become possible tomeasure the dose rate in a walking survey.
We conducted walking surveys at several points and confirmed that it is possible tomeasure the air dose rate and to create a contour map with a GIS processing system.
We published a manual for walking surveys and made the manual available to the generalpublic.

Page | 57

5. FIP5: Project for the study of promoting the proper treatment ofwaste containing radioactive materials at municipal
solid-waste incinerators
Summary
To understand changes in the migration of radiocaesium to fly ash due to changes in the
combustion temperature in the municipal solid-waste (MSW) incinerator or the addition of aradiocaesium volatility accelerator or inhibitor, we conducted demonstration tests in MSW
incineration facilities in operation. We also conducted coincineration tests of radiocaesium
bearing used filter cloth from bag filters with MSW at operating incinerators, and leaching
tests of radiocaesium in bottom ash and fly ash generated from MSW incineration facilities inFukushima Prefecture.

5.1. Purpose
Incinerating MSW that contains radiocaesium dispersed in the accident at the Fukushima
Daiichi Nuclear Power Plant causes radiocaesium to migrate to and concentrate in bottom ash
and fly ash. Bottom and fly ash generated in this way cannot be disposed of in a landfill even if
it has a radiocaesium concentration below 8000 Bq/kg, the standard set forth by law, and bottom
ash and fly ash that must be stored has thus accumulated.
【Bag Filter (BF)】

Radiocaesium removal rate of a
BF-equipped incinerator is higher
than 99.99% (MOE) Filter cloth specially fabricatedfrom glass fiber and/or Teflon
to remove more particulates,
etc., from flue gas
 Used filter cloth hasradiocaesium in/on particulates Filter cloth produces hazardous
gases upon incineration
 Used bag filter cloth iscommonly stored at theincineration facility rather thanundergoing coincineration【Incineration facility】
Most radiocaesium
is cooled from gas
state to solid CsClat the BF inlet andadsorbed onparticulates【Bag filter】
cs【Fly Ash (FA)】【boiler】【quenching
chamber】

Cooled to150-200 ℃

Cs

fly Csash

Cs flyfly Cs

ash

ash
fly
ash

Cs flyCs

Cs

fly Cs
ash

ash

fly
ash

fly Cs
ash

fly
ash

Cs

 FA has moreradiocaesium than BA,
more FA stored in thefacility than BA
 Radiocaesium in FA isreadily soluble in water

fly Csash

Csfly
ash Cs【Incinerator】
T > 800 ℃
・Cs Boiling T = 671 ℃
・most radiocaesium infurnace is in a gas state

Cs flyash

Evaporationliquefaction

Csfly
ash
Cs Cs Csfly
fly
fly ashash
Cs ash Cs fly Cs
fly Cs fly
fly
ash
ash
ash
ash

Cs
Cs

Cs

Cs
Cs

Radiocaesium

Cs【Bottom Ash (BA)】 BA has less radiocaesium than
FA and can thus institutionallybe landfilled; however, as is thecase with FA, much of BA is
temporarily stored
 Radiocaesium in BA is poorly
soluble in water

Consideration of theadequate disposal of
used bag filter cloth
1) Cut and feed used clothfor coincineration, during
which the effects ofradiocaesium andhazardous gases aremeasured2) Evaluate the safety andfeasibility of coincineration

Study radiocaesium
distribution to BA and FA
under controlled
combustion temperatureand chemical addition(1) Factors controlling theradiocaesium distribution(combustion temperature andadditives) are extracted(2) The two factors are
examined in demonstration testsa) Tests at various
temperaturesb) Close periodic ash samplingtests under normal incinerator
operationc) Combustion with additivesd) Ash radiocaesium leaching
tests

Figure 1: Issues in the waste combustion process and test study58 | Page

Although the level of radioactivity has decreased appreciably since immediately after theaccident, ash containing radioactive substances is still being generated daily by the incinerationof daily MSW. Properly treating and disposing of this ash is an urgent issue (Figure 1).
We thus decided to conduct demonstration tests to confirm the effectiveness of methods
that control the migration of radiocaesium to bottom ash and fly ash. After clarifying general
aspects of leaching characteristics of incineration ash generated in Fukushima Prefecture, wedeveloped technologies that remove radiocaesium from bottom ash and fly ash, and methods
that make soluble radiocaesium in bottom ash and fly ash hardly soluble.
Used filter cloth of bag filters with radioactive materials attached to the cloth is also
generated by incineration facilities. The proper treatment of the cloth also poses a challenge.
The coincineration of the cloth with MSW is conceivable. To confirm the feasibility ofcoincineration, it is necessary to understand the coincineration-induced change in theradiocaesium distribution to bottom ash and fly ash and its effect on the incineration facility andthe environment when coincineration is conducted. We thus conducted coincineration
demonstration tests.

5.2. Implementation Details(1) Distribution of radiocaesium to bottom ash and fly ash
Radiocaesium is known to have a tendency to generally evaporate during incineration andto transfer to fly ash rather than remaining in bottom ash. The ratios of the distribution ofradiocaesium to bottom ash and fly ash at incineration facilities in Fukushima Prefecture are
given in Table 1. The table shows that approximately 60% of total radiocaesium is transferred
to fly ash.
The literature gives five main factors that possibly govern the transfer of radiocaesium:(a) the combustion temperature, (b) the air ratio, (c) the waste composition, (d) the addition ofchemicals, and (e) the particle size of ash.
Among the factors listed, (b) the air ratio (air volume) affects various system parameters,
including the flue gas velocity, which possibly disturbs the combustion balance and affects
proper incineration, (c) the waste composition cannot be controlled, and (e) the ash particle
size is technically difficult to control. We thus focused our demonstration test on therelationships between the migration behavior of radiocaesium and (a) the combustion
temperature and (d) the addition of chemicals.

Page | 59

Table 1: Radiocaesium distribution to bottom ash/fly ash of MSW incineration
facilities in Fukushima Prefecture
Capacity
Facility

Dustcollection

Annualincineration(2011 fy)t/d

Ash generation

Radiocaesium
concentration

Radiocaesium
distribution

BA

BA

BA

FA

t/y

t/y

t/y

FA
Bq/kg

FA
%

a

105

BF

16,0352053

632

12,22049,400

45

55

b

150

EP

35,612

4797

724

7540

45,500

52

48

c

80

BF

20,2302190

1076

16,64033,900

50

50

d

30

BF

4574

381

86

1706

12,260

38

62

e

100

EP

30,111

2912

737

3920

36,300

30

70

f

120

BF

28,964

4019

747

3910

34,900

38

62

g

40

BF

12,401

2190

262

2200

17,360

51

49

h

50

BF

837

93

41

3140

13,110

35

65

i

60

BF

10,181

1342

336

639

4650

35

65

j

50

BF

8906

720

422

2269

5690

40

60

k

90

BF

16,948

1392

681

1494

6640

31

69

Note 1 Values in this table are not corrected for the amount of water or agents added.
Note 2 Incinerators at all facilities are of the stoker furnace.
Note 3 Radiocaesium concentrations were measured in July 2011.
Note 4 Dust collection method, BF: bag filter; EP: electrostatic precipitator
Note 5 Symbols for the facility here differ from those used in the text.

a) Tests for various combustion temperatures
We obtained the cooperation of Facilities A to D in conducting our tests. All facilities
were equipped with a stoker furnace.
We compared the distribution of radiocaesium to bottom ash and fly ash when thetemperature at the incineration chamber exit was raised (or lowered) 50° C from the normal
operating temperature with the distribution during normal operation.
To get a combustion chamber outlet temperature of 50° C higher or lower than that innormal operation, we raised or lowered the temperature of combustion air supplied to the
combustion chamber (i.e., primary air) by approximately 50° C from the temperature during
normal operation. The amount of combustion air (i.e., primary air) was not changed toprevent changes in the production ratio of bottom ash and fly ash due to ash blow up. Other
operating conditions, such as those relating to the furnace water spray and amount of
secondary air, differed between facilities.
Because the actual combustion temperature (in the combustion zone inside the furnace)cannot be measured, we used the temperature at the combustion chamber outlet measured incommon at each facility as an index, and evaluated the effect of the changes in thistemperature on the migration behavior of radiocaesium.

60 | Page

The test operation was continued for 1 day (i.e., 24 hours) under the same conditions in
consideration of the time needed to stabilize the combustion state and the long retention timeof bottom ash in the system.
We sampled fly ash and flue gas at least 1 hour after the establishment of the test
conditions.
As for bottom ash, because of the facility-specific long time of retention inside theincinerator and ash discharger, we predetermined, for each facility, a sampling time based on
the retention times estimated in a simple model calculation and a tracer test (where metal canswere thrown into the waste hopper and their arrival was observed at a planned sampling
point).
As an example, Figure 2 shows sampling points for bottom ash, fly ash, and exhaust gas,and estimated retention times of bottom ash inside the system for Facility A.
A) Minamisoma city clean haramachi center
Slaked Lime Silo
Farced Draft Fan

Activated Carbon Silo

Refuse Crane

steam
Air Heater

Burner

Gas Cooling
ChamberBag Filter

Charging
HopperSecondary
Combuction
Chamber

Refuse Pit Gate

Quenching
Chamber

Secondary
Combuction
Fun

Flue Gas

Auxiliary
BurnerPlatform

Furnace

Dust Conveyor

Refuse Track Scale

Fly AshInduced Draft Fan

Stack

Dust Conveyor

Refuse Pit

Dust Silo

RefuseExhaust Gas
Exhaust Gas ofclealinessAir

BottomAsh

Dust Conveyor

Fly
Ash 2

Ash
Dust
Conveyor

Ash Banka

Agent

Conveyor

Water

Conveyor

Conveyor

Retrofitting and New Construction

Figure 2: Sampling Points and System Retention Time (Facility A)
Combustion outlet

Sampling

Bottom Ash EstimatedThermometer

PointsRetention Time

We conducted measurements and analysis as shown in Table 2 for the bottom ash, flyash, and flue gas sampled as described above.

Page | 61

Table 2: Collected samples and measurement items

Analytical results of the waste composition are given in Table 3 and constitute the mostbasic information about waste. Compositional differences are thought to define the behaviorof radiocaesium in the combustion process. We cannot observe a clear relationship between
the composition of waste and the area or season that the waste was generated. In regard to
the lower calorific value of the waste incinerated, Facilities A and B had calorificvalues of 8330 to 9920 kJ/kg, while all values exceeded 10,000 kJ/kg at Facility C, which had
slightly higher caloric waste in the summer. Meanwhile, although Facility D received autumn
waste at the end of November, it had the lowest lower calorific value.

62 | Page

Table 3: Waste composition analysisb) Continuous sampling tests
As a next step, we dared not to manage operating conditions but instead implemented
demonstration tests to understand the relationship between the combustion temperature andbehavior of migration (distribution) of radiocaesium to bottom ash and fly ash during normal
operation.
We sampled bottom ash and fly ash sampling every 2 hours for 5 days continuously at
Facilities B and F. The concentration of radiocaesium of each sample was measured with a
NaI (Tl) scintillation spectrometer (hereinafter referred to as the NaI measurement). We alsomeasured the concentration of radiocaesium using a germanium semiconductor detector(hereinafter referred to as the Ge measurement).

Page | 63

The first four samples taken each day were mixed together and then divided anddistributed for Ge measurement and elemental (Cs, Na, K, Ca, Mg, Al, Si, P, and Fe) analysis.
With the data acquired, the relationship between the combustion temperature during normal
operation and migration behavior (distribution to bottom ash/fly ash) of radiocaesium was
examined.
The methods used to decide the sampling points and timings were those employed insubsection (1)-a).
c) Tests that confirm the effects of a radiocaesium evaporation accelerator and inhibitor
We conducted tests adding hydrated lime (Ca(OH)2), which is expected to promote theevaporation of radiocaesium, and tests adding bentonite (clay), which is expected to inhibit
the evaporation of radiocaesium.
We first conducted additive tests of hydrated lime and bentonite at Facility A. We
introduced hydrated lime equal to 5.5w% or bentonite equal to 2.2w% of the waste. The
materials were sprayed on the surface of each crane grasp of waste thrown into the hopper.
The first test revealed that hydrated lime had an appreciable effect on the concentrationof radiocaesium, and we subsequently conducted supplementary tests in which we added
hydrated lime. In one test, hydrated lime was added at ratios of 2.6w% and 5.5w% at thesame Facility A to check the reproducibility of the effect of hydrated lime. To confirm
whether this phenomenon was facility specific, another test was conducted at Facility D withhydrated lime added at a ratio of 2.2w%.
(2) Proper-treatment test of the used filter cloth of a bag filter
We conducted two coincineration tests of filter cloths with MSW. One was conducted at
Facility B, whose filter cloths are made of glass fiber, and the other at Facility E, whose filter
cloths are made of Teflon. Both facilities are equipped with a stoker furnace. Test conditions
were combinations of different filter cloth throw-in ratios and intervals (Table 4).

64 | Page

Table 4: Details of the used bag filter cloth coincineration test
Facility name
Filter cloth material
Run
Coincineration ratio
Filter cloth input amount
Input amount and time interval, time continued
Used filter
cloth

RUN 1
Normaloperation

RadiocaesiumRadiocaesium
Hydrogenchloride
Sulfur oxide
Flue
gas
Nitrogen oxide
Measurement
Dioxins (*2)
item
Fluorinecompounds
Radiocaesium(*1)
Bottom ash
Ignition loss (*2)
Radiocaesium
Fly ash(*1)*1) Radiocaesium samples were collected once per hour for
NaI measurement, for a total of five collections, four ofwhich were mixed into one sample and then divided for Ge
measurement.
*2) Conducted in the RUN under the most severe
conditions.

B (60 t/furnaceday)
Glass fiber
RUN 2
RUN 3
0.2%
0.4%
6.4 kg/H
12.8 kg/H(1.5/0.5 H),
3/0.5 H, 6 H
6h○

E (75 t/furnaceday)
Teflon® (polytetrafluoroethylene, PTFE)
RUN 1
RUN 2
RUN 3
0.03%
Normal0.90 kg/H
operation
0.5/1 H, 6 H
1.5/3H, 6 H
○

○
–

○
○

○
○

○
–

–
○

○
○

–
–
–
–

○
○
–
–

○
○
○
–

–
–
–
○

○

○

○

○

○
○
–
○ (fourtimes)○○○○○ (fourtimes)
○

–
○

–
○

○
○

–
○

–
○

○
○

There were two cases of the coincineration ratio(average 0.20% and maximum of 0.40%) basedon questionnaire survey results of facilities that
had actually conducted coincineration before.
Filter cloth dimensions: 164 mm φ  5250 mmL.
Weight was the manufacturer’s standard value:
2.38 kg each calculated from a density of 880
g/m2.
Radiocaesium concentration of the filter cloth
subject to coincineration: 600 Bq/kg.

The coincineration ratio was set at 0.03%,
referencing “Seiso Giho No. 8 2008 Tokyo 23
Special District Authority”.
Filter cloth dimensions: 140 mm φ  6000 mmL.
Weight was the manufacturer’s standard value:
1.71 kg each calculated from a density of 650 g/m2,
but the measured value at the facility was 2.0 kg
each.
Radiocaesium concentration of the filter cloth
subject to coincineration: 1260 Bq/kg.

Regarding the effects of coincineration on the migration behavior of radiocaesium due to
fly ash that contains radiocaesium adhering to the filter cloth, the effect of waste with glass
fiber that is difficult to combust on the combustion state, and the increase in concentration offluorine compounds due to the combustion of Teflon, we collected and analyzed bottom ash,
fly ash, and flue gas before and during the test, or collected data of measurements made by thefacility. For these items, we then compared the data obtained before inputting the filter clothand during the test and surveyed the effects. Sampling points and times were set according to
the methods described in subsection (1)-a).
(3) Understanding radiocaesium leaching characteristics of bottom ash and fly ash
We conducted leaching tests for 15 pairs of bottom ash and fly ash sampled from six
incineration facilities, Facilities A to F. The tests were based on the “JIS K0058-1 ‘As is’ Stir
Test” method of placing 250 g of a sample as is into a container, adding 10 times the amount(L/kg) of pure water, and then stirring the upper liquid portion with a propeller.

Page | 65

5.3. Results and Discussion(1) Distribution of radiocaesium between bottom ash and fly asha) Tests for different combustion temperatures
Data on the migration and distribution of radiocaesium gained from tests are given in
Table 5.

Table 5: Combustion temperature and migration of radiocaesium for each facility and each test

Facility

Test
date

Test

Primary
airtemp

Combustion
chamberoutlet temp
°C

A

6/23
6/24
6/26
6/27
7/2
7/3
10/14

A
Add.

10/16
10/17

B

C

D

7/8
7/9
7/10
7/11
7/28
7/29
7/30
7/31
11/25
11/26
11/27
11/28
11/29

Standard 1
Standard 2
High temp 1
High temp 2
Hydrated lime
2.4%
Bentonite 2.2%
Standard
Hydrated lime
2.6%
Hydrated lime
5.5%
Low temp 1
Low temp 2
High temp 2
High temp 2Standard 1
High temp 1
High temp 2Standard 2
Standard 1
High temp 1
High temp 2Standard 2
hydrated lime
2.2%

Radiocaesium
concentration
Bq/kg(measurement
value)
Bottom
Fly
ash
ash
1580
8300
1750
10300
2020
10800
1460
13500

Radiocaesium concentration
Bq/kg (corrected value (*1))

Distribution
ratio % ofradiocaesium tofly ashFlyash/bottom
ashradiocaesium
concentration
ratio (*2)

Bottom ash

Fly ash

1900
2100
2500
1900

13000
16000
17000
21000

60
63
61
72

6.8
7.6
6.8
11.1

125
121
183
189

904
912
964
950

119

923

840

14800

1100

23000

84

20.9

123
121

940
904

1990
1260

14600
14500

2400
1400

23000
20000

69
76

9.6
14.3

116

891

920

15700

1200

22000

83

18.3

116

904

540

10400

650

15000

84

23.1

101
103
200
194
52
100
100
52
178
129
134
177

855
842
946
956
933
931
924
937
880
867
873
883

1020
900
940
590
930
1110
1740
1490
480
480
453
530

5700
4600
5100
4700
7800
6400
9600
9500
1590
1450
1470
1250

1200
980
1000
630
1100
1300
1800
1700
430
430
400
470

6800
5500
6100
5600
12000
15000
15000
2900
2600
2600
2200

68
67
68
76
71
64
63
64
54
52
54
46

5.7
5.6
6.1
8.9
10.9
7.6
8.3
8.8
6.7
6.0
6.5
4.7

178

893

410

1280

360

2300

53

6.4

(*1) Measured values were corrected for flue gas treatment agents and water added during the process.
(*2) Corrected values were used.

The tests were conducted in four facilities, but we were unable to obtain a combustion
chamber outlet temperature higher than that of standard operation during high-temperature
operation at Facility C. Additionally, at Facility D, we were unable to obtain a combustion
chamber outlet temperature lower than that of standard operation in low-temperature
operation.

66 | Page

Facilities A and B ran for two days at high combustion temperature throughhigh-temperature operation. A high rate of radiocaesium distribution to fly ash was achievedon the second day. Linear approximations with exclusion of data of the first day give an
increased radiocaesium distribution rate of 2.6% (Facility A) and 0.8% (Facility B) per~10 °C increase in the incineration temperature (Figures 3 and 4).

(Facility A)
Hydrated Lime 2.4%

Bentonite
High Temp 2Standard 2

Standard 1

High Temp 1

Combustion chamber outlet T (℃)

Figure 3: Rate of distribution of radiocaesium
to fly ash versus the combustion chamber outlet
temperature (Facility A)

Radiocaesium distribution ratio to fly ash (%)

Radiocaesium distribution ratio to fly ash (%)

To see the variation in temperature and the migration status of radiocaesium before and(Facility B)

High Temp 2

Low Temp 2
Low Temp 1

High Temp 1

Combustion chamber outlet T (℃)

Figure 4: Rate of distribution of radiocaesium
to fly ash versus the combustion chamber
outlet temperature (Facility B)

after changing the combustion temperature conditions from standard to high-temperature
operation, we sampled bottom ash and fly ash every 2 hours for 2 days during the test at
Facility B, and conducted a NaI measurement. Results confirmed that with the change inoperation mode from low-temperature operation to high-temperature operation, thecombustion chamber outlet temperature increased approximately 100 °C, from 850 to 950 °C,
and the fly ash/bottom ash ratio of the radiocaesium concentration increased along with theincreasing temperature (Figure 5).

Figure 5: Combustion chamber outlet temperature and radiocaesium concentration ratio(Facility B)

Page | 67b) Continuous sampling test
Figures 6 (Facility B) and 7 (Facility F) show the combustion chamber outlet
temperature, NaI-measured radiocaesium concentration in bottom ash and fly ash, ratio of theradiocaesium distribution to fly ash based on NaI measurement, and ratio of the radiocaesium
distribution ratio to fly ash based on Ge measurement.

Combustion
chamber outlet
T (℃, right axis)
燃焼室出口温度(℃,
右端軸)

1000

950

900

850

800

750

Radiocaesium concentration (Bq/kg)

Radiocaesium distribution ratio to FA (%)

100

Sample no.
Radcaesium concentration in BA
Radiocaesium distribution ratio to
FA (calc. from NaI measurements)

Radiocaesium concentration in FA
Radiocaesium distribution ratio to FA (calc. from Ge
measurements)

Figure 6: Radiocaesium concentration in bottom ash and fly ash from NaI measurement,
radiocaesium distribution ratio from both NaI and Ge data, and combustion
chamber outlet temperature (dry basis, Facility B)

950
900

Radiocaesium concentration (Bq/kg)

Radiocaesium distribution ratio to FA (%)

850

Sample no.

Radiocaesium
Concentration in;
BA
FARadiocaesium distribution ratio
to FA (calc. from NaI
measurements)

Radiocaesium distribution ratio to FA (calc. fromGe measurements)

Figure 7: Radiocaesium concentration in bottom ash and fly ash from NaI measurement,
radiocaesium distribution ratio from both NaI and Ge data, and combustion
chamber outlet temperature (dry basis, Facility F)

68 | Page

It is difficult to see a clear relationship between the combustion chamber outlet
temperature and the distribution of radiocaesium to fly ash.
Looking at the plots of the temperature and the ratio of the radiocaesium distribution to
fly ash based on NaI measurement data (Figures 8 and 9), the rising combustion chamber
outlet temperature at Facility B was accompanied by a rising ratio of the radiocaesium
distribution to fly ash. Sudden drops in temperature may correspond to the inputs of sewage
sludge, and it should be noted that the waste composition has also largely changed. The rangeof variation in the outlet temperature of the combustion chamber of Facility F was small, andno clear proportional relationship between the radiocaesium distribution ratio and combustion
chamber outlet temperature was observed.
Radiocaesium
distribution ratio to FA, %飛灰への分配率（％）

9080

y = 0.0632x + 5.7782
R² = 0.123

70
60
50

40
30
20
10
0
700

750

800

850
燃焼室出口温度（℃）

900

950

1,000

Combustion chamber outlet T (℃)

Radiocaesium
distribution ratio to FA, %飛灰への分配率（％）

Figure 8: Combustion chamber outlet temperature versus the ratio of theradiocaesium distribution to fly ash (Facility B), with theradiocaesium concentration obtained by NaI measurement

90
80

70
60
50

y = -0.0836x + 143.29
R² = 0.0506

40
30
20
10
0
800

850

900

950

1,000

燃焼室出口温度（℃）
Combustion
chamber outlet T, ℃

Figure 9: Combustion chamber outlet temperature versus the ratio of
the radiocaesium distribution to fly ash (Facility B), with theradiocaesium concentration obtained by NaI measurement

Page | 69

The data taken continuously over 5 days for Facility F show a weak positive correlation
between the ratio of the radiocaesium distribution to fly ash and the waste basicity (Figure 10),
but no correlation with the chlorine content can be observed (Figure 11). The basicity of theRadiocaesium distribution ratio to FA (%)

waste was calculated from the chemical compositions of bottom ash and fly ash.

Basicity of waste (CaO/SiO2)Radiocaesium distribution ratio to FA(%)

Figure 10: Basicity of the waste calculated from the chemical composition of bottom
ash and fly ash versus the ratio of the radiocaesium distribution to fly ash(Facility F)

Calculated chlorine content in a ton of waste

Figure 11: Chlorine content in the waste calculated from the chemicalcomposition of bottom ash and fly ash versus the ratio of theradiocaesium distribution to fly ash (Facility F)c) Tests that confirm the effects of a radiocaesium evaporation accelerator and inhibitor
An appreciable rise in the ratio of the radiocaesium distribution to fly ash (a 9.3% rise in
the distribution ratio per 1% additive rate) was observed in the first hydrated-lime additive
test at Facility A, but the inhibiting effect of bentonite was not confirmed (Figure 3).
We conducted additional tests to confirm the effects of adding hydrated lime, and acertain effect was confirmed at Facility A but it was not as great as in the first test. It was
confirmed that there was no effect at Facility D (Figure 12).

70 | Page

100

Radiocaesium
distribution ratio to FA (%)
飛灰へのＣｓ分配率（％）

90

80

70

60
Low-T 2
Low-T 150Standard 1+2.2% Ca(OH)2

Standard 2
40
800

850

900

950

1000

燃焼室出口温度（℃）
Combustion
chamber outlet T (℃)

Figure 12: Effect of adding hydrated lime on the ratio of the radiocaesium
distribution to fly ash (Facility D)

According to a literature survey, higher basicity of the incinerated matter should
accelerate the evaporation of radiocaesium. Basicity of the waste calculated from thechemical analysis of bottom ash and fly ash conducted at Facilities A to D is given in Table 6.
The table shows that the basicity of waste at Facility A was lower than that at other facilities.
It is probable that the obvious effect observed at Facility A was due to adding thebasicity-increasing agent, hydrated lime, to low-basicity waste. Yet in the case of Facility D,
it is possible that the basicity-increasing agent was added to waste whose basicity was high toa certain degree, and the hydrated lime thus did not promote the evaporation of radiocaesium.
In this demonstration test, we had tight operating conditions that differ from theconditions of usual operation, and it was thought that the operations increased theradiocaesium concentration in flue gas. We therefore conducted measurements of flue gas anddioxins. As a result, no radiocaesium was found in the flue gas. Furthermore, the dioxin
concentration in flue gas and ignition loss values of bottom ash met the criteria of relevant
regulations.

Page | 71

Table 6: Basicity of waste calculated from the chemical compositions of bottom ash and fly ash

Calculation of basicity for the days on which hydrated lime was added. We used the average of analyzed
values of the dates 6/26 and 6/23 for 7/2, the analyzed values of the date 10/14 for 10/16 and 10/17, and theaverage of analyzed values of the dates 11/25 and 11/26 for 11/29.

(2) Proper-treatment test of the used filter cloth of a bag filter
Coincineration of used filter cloth with MSW was confirmed safe and feasible under theproper management of the coincineration ratio.
Regarding many measurements that we made, used filter cloth coincineration did notaffect the measurements but increased the concentration of radiocaesium in ash (Table 7). This
increase was observed at Facility B and no increase was observed at Facility E. The increase isthought to be caused by a change in the radiocaesium concentration in MSW coincinerated
rather than the input of used filter cloth. This is supported by two pieces of evidence. First, theincrease was higher than the value calculated from the radiocaesium concentration of the input
filter cloth. Second, the increased values remained within the range of variation of themeasurements that the facility made in 2015. No radiocaesium was detected in flue gas and noeffects of coincineration on flue gas were confirmed. Table 8 presents the case for Facility E.
Table 7: Radiocaesium concentration in bottom ash and fly ash

72 | Page

Table 8: Radiocaesium in flue gas

There were no changes in the ignition loss of bottom ash, harmful acidic substances, anddioxins in flue gas at either facility. These items are conceivably affected when combustion
conditions deteriorate (Table 9).

Table 9: Harmful acidic substances and dioxins in flue gas, and ignition loss of bottom ash

Page | 73(3) Understanding radiocaesium leaching characteristics of bottom ash and fly ash
To understand the general nature of radiocaesium leaching from bottom ash and fly ash,
we conducted leaching tests for the ash from six MSW incineration facilities in Fukushima
Prefecture. Result shows that leaching from bottom ash was limited (less than 1.4% to 16%),
as it is generally considered to be, but we also confirmed that sometimes there was leaching at
a very high ratio (47% to 83%) from fly ash (Tables 10-1 and 10-2). The results widely vary. A
pair of ash samples from Facility D was the most interesting, having the lowest leaching rate of
47% for fly ash and the highest leaching rate of 16% for bottom ash.
Fly ash referred to here was raw ash collected using a bag filter, with no treatment, suchas the addition of chelating agents, conducted.

Table 10-1: Radiocaesium leaching test results (1)Table 10-2: Radiocaesium leaching test results (2)74 | Page

Test results thus far obtained are summarized in Table 11.

Table 11: Summary of test results